Armbruster (2004) determines that a clade consisting of Delturus and Hemipsilichthys
(Upsilodus is a synonym of Hemipsilichthys) form a monophyletic group sister to all other loricariids except Lithogenes. A manuscript is currently in preparation by myself, Roberto Reis, and Edson Pereira, so limited information is provided here. In my thesis (Armbruster, 1997), I mistakenly referred to the juvenile Delturus I had available
as Upsilodus.COMPARISONS

Both genera can be separated from all other loricariids by the presence
of a postdorsal ridge made up of raised, median, unpaired plates and the
presence of an adipose fin membrane.
Upsilodus
can be separated
from Delturus by not having the anterior plates of the ridge contacting
the lateral plates (juvenile Delturus
also have this condition)
and by having a rectangular (vs. V-shaped) spinelet.